1. Field of the Invention
The present invention relates to a direct-coupled grounded-base amplifier for use in an information processing device and a semiconductor integrated circuit device.
2. Related Background Art
As a conventional direct-coupled grounded-base amplifier used in a semiconductor integrated circuit, the circuit in FIG. 1 is known.
Referring to FIG. 1, the circuit is composed of a power supply line 1, a GND line 2, a power supply 3 for applying a reference voltage to a base of a grounded-base amplifier 12, resistors 4a to 4c and 5 to 8, a condenser 10, NPN transistors 11 to 14, constant current sources 17 to 21 and a condenser 25 mounted outside of an integrated circuit (IC).
The direct-coupled grounded-base amplifier shown in FIG. 1 is constituted by two grounded-base amplifying circuits. In other words, signals amplified by a first amplifying circuit, including the NPN transistors 11 and 12, the resistors 4a, 4b, 5 and 6 and the constant current sources 17 and 18, are further amplified by a second amplifying circuit, including the NPN transistors 13 and 14, the resistors 4c, 7 and 8, the constant current sources 20 and 21 and the condenser 25, and output from the NPN transistor 15.
However, in the above conventional circuit, as shown in FIG. 1, it is necessary to mount the capacitor 25 outside of the IC in order to equalize the direct potentials at both ends of the input resistor 7 of the grounded-base amplifier 14. Therefore, the PIN number of the IC is increased, the band is deteriorated by PAD parasitic capacitor, and furthermore, the number of components are increased.